[yt-dev] Field Parameters Bug

[Matthew Turk]

Hi Hilary,

Maybe we ought to have a registry of known field parameters,
affiliated with dimensions.  A while back I looked at the known ones,
and there were not many in use.  It might be relatively
straightforward to set up a simple registry.  My concern is then that
individuals wanting to define their own are going to run into an issue
of the behavior changing, not knowing how to fix it, and so on.

Alternately, we could use a default parameter in those failing fields.
Or, we could add an argument to the add_field call of the dimensions
of the field parameter.

-Matt

On Wed, Oct 1, 2014 at 3:22 PM, Hilary Egan <hilaryye at gmail.com> wrote:
> Hi all,
>
> I've encountered a bug with this example in the docs of getting/setting
> field parameters of a dataset for use in a derived field. The example works
> fine for known yt field parameters like bulk_velocity, but if you change
> every instance of "bulk_velocity" to "my_bulk_velocity" (sample script),
> then it breaks with this error.
>
> It seems as though this breaks because `has_field_parameter` always returns
> True, and there is no way to know ahead of time what units a user-defined
> field parameter will take, so the mock field data can't be set up correctly.
> Nathan suggested via IRC that this might necessitate creating a way to
> register user-defined field parameters, but it's probably worth
> brain-storming about if anyone else has any other suggestions!
>
> -Hilary
>
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